OK, I tried the VP180 in the vertical position against an M80v2. I simply placed both speakers in front of my AV unit and made changes to the Denon so I had a mono signal(what a PITA). I listened to various types of music and I found the M80 to have a wider soundstage, that is to say the music didn't seem to come from just the speaker while the VP180 had a similar effect but not as much. I suspect this is due to the different driver configuration. I think the differences would be greatly diminished once played with a left and right speaker for multichannel duties but YMMV.
Tony, sorry I forgot to respond to your question about an M22 center vs the M2. IMO there is little difference. The M22 will allow a 60hz crossover if so desired and but it really doesn't have the size to handle those frequencies with any real authority, not like the VP180 or floorstanders do. If you have bookshelf speakers for L/R then by all means run the same speaker across the front as it will yield a truly seemless soundstage, if the M22 is too tall then the M2 will fill in nearly perfectly, I doubt most would ever notice any difference.
